The other day Ruth asked me where the
step- in words like
step-father comes from. I had to confess that I didn't actually know, but I guessed that it signified that the relationship was a metaphorical step away from a biological one. But it turns out my off-the-cuff guess was totally wrong; it comes from
a different root meaning 'bereft'.
Stepchild originally meant 'orphan' (or a child who had lost at least one parent), and words like
stepfather meant 'father to an orphan' and so on. The
OED says, "The concept of orphanage has recently ceased to be essential to the meaning of the
step- combinations. Consequently, the relationships of
step-brother, -
sister, etc., may be considered to refer reciprocally to children of a later as well as a former marriage: i.e. step-brother = half-brother, etc. A step-parent may be created by marriage to a divorced or a bereaved person."